A category of machines utilizing a continuous chain digging element is widely used in the earthmoving arts. These so called chain saw excavating machines range from about ten horsepower to several hundred horsepower and are generally used in trenching applications for laying pipe or cable. These machines, examples of which are manufactured by TESMEC USA, Inc., of Mansfield, Tex., and Vermeer Manufacturing Company of Pella, Iowa, are mounted on crawler track undercarriages for purposes of both stability and flotation, however pneumatic tires may also be used.
TESMEC trencher models TRS 900 and TRS 1000 have optional, interchangeable booms so that either a chain saw or a circular rock saw may be used as the digging element, depending upon the application. Rock saws are considered to be better adapted to digging rock and hard formations and are used for narrow cable laying trenches, while chain saws are normally used for the wider, deeper trenches needed for laying pipe.
These machines are generally more productive when working in the softer formations. Excavation of the harder formations is more difficult and costly in terms of time, power consumption and attrition. Very hard, specialized cutting teeth, such as Part Number CCT-735-HBR, made by the Carboloy Construction Products of Bristol, Va., have been developed which improve productivity in these hard materials, within limits.
To those skilled in the art it is known that tooth vibration offers great potential for increased productivity as well as the capability of working in harder materials. Various studies that compare the efficacy of digging teeth, with and without vibration, have shown that dramatic production increases can be achieved with a vibratory system. Efforts to devise practical means for realizing such benefits with a vibrating chain saw have been thwarted by unacceptably rapid chain wear and the deleterious effects of the vibration to the supporting structure.
An object of the present invention is then, to provide a practical means for vibrating the cutting teeth while minimizing the factors which induce chain wear.
Isolation of this vibration so that it is confined to to the chain saw boom assembly is essential to any practical design. Without such isolation, the vibratory forces are as destructive to the machine itself as to the formation it is excavating. A second object of the present invention is therefore, to provide suitable vibration isolating support means for the vibrating chain saw boom assembly. This support means must not only carry the high crowd and chain pull forces involved in the penetration of hard formations, but must also yield and allow the displacements of vibration so as to isolate the excavator main frame from the effects thereof.
Because of the shock and vibration forces attendant to cutting rock, normal operating conditions are such that chain saw excavators, without the invention, require an unusual degree of maintenance. Another object of the invention therefore, is to moderate these forces and reduce their effects on the excavator main frame and other components.